Cutting-edge grinding solution

Topic of the month

SAACKE was looking to achieve a significant reduction in changing times for the smooth loading of various workpieces into the grinding center of type UW I F. The company thus opted for robot-based automation of the grinding process.

Today, a KUKA robot from the KR AGILUS small robot series in a waterproof design ensures fast and precise transfer and unloading of workpieces and has thus optimized the capacity utilization of the tool grinding machine.

“For the tool grinding center of type UW I F, we were looking for an automated solution which works with speed and precision. To ensure maximum flexibility, it was our aim to integrate a robot capable of performing various tasks into the system,” explains Gerhard Kopp, Head of Design at SAACKE’s Machines Division. When searching for a suitable partner, SAACKE chose KUKA. “The price/performance ratio as well as the flexible robot programming won us over,” adds Kopp.

The Design, Customer Service and IT departments were all involved in designing the fully automated system. This was to ensure, on the one hand, that the work processes were perfectly matched to customer requirements, and on the other, that the system would be easy to operate. The developers had to account for a number of special aspects in the design of the system. In order to be able to reliably complete the various tasks within the desired cycle time, for example, the robot was equipped with a double gripper.

A special program was developed for this purpose. With this program, the workpiece carrier can be emptied and loaded again in a single work step – a significant factor in boosting the efficiency. The robot cell was also designed to allow for it to be converted for other workpieces.

“The integration of the robot into the machine sequences required not only adaptation of the machine enclosure, but also development of a suitable interface between the robot and machine controllers,” notes Kopp, in describing a further challenge that has been successfully mastered.

The six-axis KUKA KR 6 R900 sixx WP removes the workpiece to be machined (e.g. an indexable insert or a shank tool) from a pallet in the robot cell. Indexable inserts are mounted on a pin. Following this, it positions the workpiece in front of the door of the cell, which then opens automatically.

The robot arm then moves through the open door to the grinding device outside of the robot cell, where a machined workpiece is already located during ongoing operation. Using the second gripper, the robot picks up this workpiece and then loads the new workpiece with a quick rotation of the gripper arm. Machining of the new workpiece with the type UW I F tool grinding machine begins.

In the meantime, the robot arm returns to the robot cell. There, the machined workpiece is cleaned in the blowing station and then set down again on the pallet before the robot grips the next workpiece to be ground and the work sequence is repeated from the beginning.

Cells with the KUKA KR 6 R900 sixx WP have been in operation for SAACKE customers since June 2015. The robot from the KR AGILUS series has a payload capacity of six kilograms and works extremely precisely both with indexable inserts weighing just a few grams and with shank tools of up to 2.5 kg. With a reach of 900 mm, the robot covers the entire workspace ideally. The extremely robust waterproof variant of the small robot is used in the cell.

It features stable stainless steel covers, resistant surface treatment and additional seals in the interior, enabling it to be used in a machine tool environment. This prevents ingress of cooling lubricant and grinding oil into the robot – a highly important factor for SAACKE in selecting the KR AGILUS WP, which meets the increased IP 67 protection rating.

“To be sure, the robot is not directly exposed to the spray of cooling lubricant. However, cooling lubricant and oil mist is indeed generated during the workpiece change,” explains Kopp. As a result, damage to the seals, cables and hoses or the measurement system could therefore occur without special protection.

SAACKE already presented the pilot version of the robot-based automation at the 2015 EMO trade fair in Milan. “The positive customer reaction was confirmation to us that this offer represents an important addition to our portfolio,” summarizes Kopp. The robot fully meets SAACKE’s expectations in terms of speed and flexibility.

Thanks to a shortened cut-to-cut time – defined in VDI guideline 2852 as the time between the unloading of a tool and introduction of a subsequent tool to the same machining position – the capacity utilization of the machine has been substantially improved. Furthermore, the reliable procedure has enabled the operator control requirements of the machine to be significantly simplified.

“This solution makes it possible to implement large-scale series production of workpieces without any difficulties,” sums up Kopp. As a result, SAACKE is planning to adapt the robot-based automation for other machine types as well in the future. This allows, for example, for the integration of further functions such as laser marking of the workpieces.